An EW source said director Bill Condon might use digital effects like those seen in "The Curious Case of Benjamin Button" to age the actress. During the last installment of "The Twilight Saga," Renesmee grows to the age of 17 in only seven years.

Mackenzie has previously appeared on the small screen in one episode each of "FlashForward" and "'Til Death."

In more "Twilight Saga" casting news, according to Deadline, former "Lost" star Maggie Grace has landed the role for villain Irina, a member of the Denali coven and serious threat to Bella and The Cullens.

"Breaking Dawn," which will be released in two installments, is slated to start filming in November.

When contacted by EW, Summit would not comment on the report that Mackenzie was being considered for the role. Likewise, when contacted by Access, Summit would not comment on the Maggie Grace casting.